225 ILCS 470/24
Except as otherwise provided in this Act, any commodity in package form introduced or delivered for introduction into or received in intrastate commerce or kept, offered or exposed for sale in intrastate commerce shall bear on the outside of the package a definite, plain and conspicuous declaration of (1) the identity of the commodity in the package, (2) the net quantity of the contents in terms of weight, measure or count, and (3) in the case of any package kept, offered or exposed for sale, or sold elsewhere than on the premises where packed, the name and place of business of the manufacturer, the packer, or the distributor as may be prescribed by regulation issued by the Director. In relation to such declaration of net quantity, neither the qualifying term "when packed" or any words of similar import, nor any term qualifying a unit of weight, measure or count which exaggerates the amount of commodity in a package, shall be used. Any package that is introduced or delivered for introduction into or received in intrastate commerce or kept, offered, or exposed for sale in intrastate commerce may be opened for inspection without cost to the Department for the purpose of determining the net contents. All opened products shall remain at the point of inspection. Also in relation to such declaration of net quantity, the Director shall by regulation establish (a) reasonable variations to be allowed, which may include variations below the declared weight or measure caused by ordinary and customary exposure, only after the commodity is introduced into intrastate commerce, to conditions that normally occur in good distribution practice and that unavoidably result in decreased weight or measure, (b) exemptions as to small packages, and (c) exemptions as to commodities put up in variable weights or sizes for sale intact and either customarily not sold as individual units or customarily weighed or measured at time of sale to the consumer.
225 ILCS 470/24